Magnetic instrument



Sept. l, 1945.

V. W. BREITEN STEIN MAGNETIC INSTRUMENT Filed July 27, 1940 2 Sheets-Sheet 1 "mmm ummm/ifi,

Sept 11 1945 v. w. BREITENs-rm 2,384,529

MAGNETIC INSTRUMENT Filed Julyzv, 1940 2 sheets-sheet 2 mss.'

Patented Sept. 11, 1945 MAGNETIC INSTRUMENT Victor W. Breitenstein, Chicago, lll., assigner to r Illinois Testing Laboratories, Inc., Chicago, lll.,

a corporation of Illinois Application July 27, 1940, Serial No. 347,839

4 Claims.

The present invention relates to magnetic instruments, and is particularly concerned with magnetic instruments adapted to be used for indicating the presence of magnetic metal, measurement of thickness, indication of thickness limits, or the like.

One of the objects of the invention is the provision of an improved magnetic instrument which is adapted to be used for the measurement of thickness of various articles, such as coatings, papers, or other relatively thin articles which are otherwise relatively difficult to measure.

Another object of the invention is the provision of an improved magnetic instrument which is adapted to indicate limits of thickness, or which may be used for comparing the thickness of dierent articles.

Another object of the invention is the provision of an improved magnetic Yinstrument which is adapted to be used as a magnetic metal indicator so that it may be employed by the wardens or guards of prisons for detecting the presence of weapons or tools or other articles of a dangerous nature which are generally made of magnetic metal.

Another object of the invention is the provision of a magnetic instrument of the class described, which is sturdy, accurate, capable of being calibrated in various ways, and which may be usedl for a long period of time without necessity for repair.

Another object of the invention is the provision of an improved magnetic instrument oi the class described, which does not require any electric energization in the form of batteries or other connections to supply circuits, and which may, therefore, be embodied in a portable form adapted to be used at any time or place.

Another object of the invention is the provision of a small self-contained pocket size instrument adapted to effect measurements of thickness, or to give indications of presence of magnetic metal. 4

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters or reference indicate similar parts throughout the several views.

Referring to the drawings, of which there are sheets accompanying this specification,

Fig. 1 is a View in perspective of a device embodying my invention;

Fig. 2 is a plan view of the face of the instrument indicating unit when it is removed from the housing;

Fig. 3 is a side elevational view of the indicating unit;

Fig. 4 is a lower end elevational view of the indicating unit;

Fig. 5 is a diagrammatic illustration of the indicating unit, shown in connection with an article, they thickness of which is to be measured with a block or plate of magnetic metal which is placed on the lside of the article to be measured, opposite to the indicating unit.

Fig. 6 is a fragmentary elevational view in partial section, showing an adjustment for engagement with the material to be measured;

Fig. 7 is another similar fragmentary view of a modication.

Referring to Fig. 1, il! indicates the magnetic instrument, which is preferably enclosed in a housing, indicated at l l. This housing may consist of a box-like metal member made of nonmagnetic metal, such as aluminum, or of insulating material, such as a molded condensation compound; and the housing i l is preferably provided with the plane front and rear panels l2 and plane side panels I3, all of these panels being integrally joined together to form a box-like member open at each end.

The ends may be closed by means of a metal plate it of non-magnetic metal, such as brass, which may be nickel plated, and secured in place ,by a plurality of screw plates l5, passing through When the device is provided with signal lights.'

the housing il has its front wall I2 formed with the window apertures i9 and 2li, which are closed by means of the colored glass members 2l and 22. For example, the window 2l may be green, and the window 22, red, for the purpose of indicating the limits of measurement when the device is used as a thickness limit indicator.

The front wall l2 is also preferably provided with an arcuate window opening 23, which is covered on the inside by a pane of glass 24, and which exposes a dial 25, provided with suitable scale indicia for indicating the thickness of the material to be measured.

26 indicates an aperture in one side of the housing at the bottom for receiving a threaded sleeve 21,; which supports an adjustment screw, the purpose of which will be later described in detail.

The indicating unit, which is best illustrated in Figs. 2 to 4, preferably includes a supporting plate 30, upon which the complete unit is so mounted that it may be removed from the housing as a unit and slid out of either end of the housing.

This plate 30 is preferably of brass or other non-magnetic material, and provided on its rear side with a plurality of internally threaded sleeves 3|, which are engaged by screws passing through the rear wall of the housing and threaded into the sleeve 3i to secure the unit in the housing.

At its upper end the supporting plate 30 preferably supports a 'dial plate 32 consisting of a rectangular metal plate which is covered with a layer'of paper having an arcuate dial with scale divisions. The dial plate 32 may be secured in place by a pair of bolts passing through the dial plate and through spacing sleeves 33.

The plate 30 is preferably provided with an insulating bed plate 34 for the purpose of bringing the magnet 35 up to the proper level.

The magnet 35 preferably consists of a magnet of substantially U shape, having a pair of parallel legs 36, 31 joined by a yoke 38, and it may be secured on the supporting plate 30 by a non-magnetic cross bar 38', which engages the magnet, and which is secured to the plate by a through screw bolt 39 threaded into a threaded sleeve on the plate 30.

The magnet 35 is preferably disposed at one side of the supporting plate 30 so that its leg 36 is centrally located on the plate, and the leg 36 extends into a non-magnetic rframe 40, which is provided with a pair of standard jewels supported by the screws 4|, 42, and locked by means of lock nuts 43.

'I'he frame 40 consists of a rectangular metal frame made of straps of brass, which is provided with laterally projecting flanges 44 that may be secured to the base 30 by screw bolts 45. The base 30 is cut out at 46 surrounding the lower jewel screw 42 and lock nut 43.

Pivotally mounted in the jewels carried by the screws 4|, 42 the device is provided with a spindle 41, preferably of magnetic metal, such as steel, and the spindle 41 is soldered or otherwise secured to the edge of a rectangular vane48 of magnetic metal, such as soft iron or Alnico.

The material of which the permanent magnet 35 is made is also preferably Alnico or some magnetic metal of high permeability.

The spindle 41 also has secured to its opposite side a light aluminum wire needle 49, which extends longitudinally of and above the leg 36 of the magnet and has its upper end moving above the scale divisions 25 of the dial.

An extension 50 of the needle Wire, extended downward in the opposite direction to the needle, is provided with a counterweight 5| of solder or other suitable material so that the needle, vane, and spindle are in a state of balance.

'I'he vane 48 extends in such a direction with respect to the spindle 41 that it is substantially tangential to the lines of magnetic flux which extend from the leg 36 to the leg 31 when the instrument is not being used.

This may, however, be adjusted by means of a screw bolt 52 of magnetic metal, which is supported in the threaded sleeve 21 of the housing 'I'he screw bolt 52 is located immediately adjacent the leg 31, and provides an extension for the leg 31 in the direction of the leg 36. As the screw bolt approaches the leg 36 it causes the flux to extend more directly across the space between the pole pieces and tends to move the vane 48 upward and to move the needle 49 toward Thus, the screw 52 provides a convenient form of zero adjustment, or the needle 43 may be adjusted by means oi it to the middle of the dial. for use with contacts and signal lights, as a thickness limit indicator. K

In some embodiments of the invention the spindle 41 may be provided with a return spring secured to the spindle and the frame 40 to bias the needle 49 back to the zero position.

The dial plate 32 may have a pair of wires 53 lsoldered to its lower edge and provided with cured to it and extending transversely to the di,

rection of movement of the needle to effect a damping of the needle.

In some embodiments of the invention the sup'- porting plate 30 may also support an insulating plate 56 which extends from one side of the unit to the other above the lower part of the magnet and is adapted to support the contact posts 51, 58, which have adjustable contact screws 59, 69 for engagement with the needle 49 at-predetermined limits of movement.

These contact posts 51, 58 are connected by wires to the bulbs 6|, 6|', which are located below the green and red windows 2|, 22, and the circuit is completed by the needle, which is grounded to the metal plate 30. Of course, a small standard dry cell may be housed in the housing behind the dial plate 32, and may have one of its terminals connected to ground, and the other terminal connected to the contact posts 51, 58 for energization of the lights 6I, 6|.

In other embodiments of the ,invention the contacts 59 and 60 may control a thermionic amplifying circuit or a core reactor amplifying circuit, which in turn controls machinery or other devices.

When the device is used as a thickness limit meter, one 0f the limits of thickness is indicated by engagement of the needle 49 with the oontact 60, illuminating the light 6| behind the green window 2l. The other limit of thickness is indicated when the needle 49 engages the contact 59, illuminating the light 6| behind the red Window 22.

The operation of the thickness measuring instrument is diagrammatically illustrated by Fig. 5, in which 62 indicates a piece of paper or other material, the thickness of which is to be measured; and 63 indicates a block of magnetic metal, such as soft iron, upon which the material 62 to be measured is placed.

The lower end of the housing of the instrument is then pressed against the paper, and under these conditions the magnet and vane are spaced from the block 63 of magnetic metal a distance which depends upon the thickness of the material 62.

'Ihe ux emerging from the legs of the permanent magnet 35 takes the path of least resistance, and a large proportion of the flux is gentially to the curved lines of iiux within which it is located. Thus, the position of the needle varies with the spacing of the keeper 63 from the ends of the magnet 35. This spacing is, of course,

dependent upon the thickness of the material to be measured. The scale divisions of the dial may be calibrated in any way, and I have found that the present instrument is capable of making measurements of thickness with a good degree of accuracy,

Referring to Fig. 6, this is a modification which is adapted to be used under conditions where a higher degree of accuracy is desired. The support of the material to be measured between the plane surfaces of the bottom of the housing and the keeper si)l is not conducive to the highest degree of accuracy because the spacing between these members depends upon the accuracy of the plane surfaces.

Therefore, in another embodiment of the invention the bottom plate of the housing may be provided with a three point support for engaging the keeper 63 in the form of two xed downwardly projecting metal legs 64 and one adjustable downwardly extending' non-magnetic metalleg S5.

Each of these metal legs may be provided with a cup at its outer end, which is used to secure a hardened ball 66 to the leg for the purpose of providing a uniform surface, which is not subject to excessive wear.

The adjustable leg B'comprlses a threaded rod, which may be made of non-magnetic metal and may be threaded into the lower housing plate I6, and may extend through the housing and an aperture in the upper housing plate I4, where its upper end will be provided with an adjustment knob, which may have scale indicia cooperating with a pointer on the housing. v

In other embodiments of the invention, the rod S may be provided with an enlarged disc immediately inside the lower cover plate having its edge projecting through a slot in the housing to permit the actuation of the rod 65.

The adjustment rod 65 is preferably located adjacent the vane 48, and the three legs 64, 65 merely determine the spacing of the instrument assembly from the plane surface of the block of magnetic metal 63, with which it is used.

The magnetic instrument would then rest upon the material 62 to be measured, by means of the three legs 64-65, and the thickness would be measured at the point where the adjustable leg 65 makes its point of engagement with the material to be measured.

The zero adjustment of the needle may be set by means of an adjustable leg 65 when the instrument is directly engaging the keeper 63, and a higher degree of accuracy can be attained because the thickness is actually measured at one int. l l

It will thus be observed that I have invented an improved magnetic: instrument which may be used for comparing thickness, for indicating limits of thickness, or for effecting a measurement of the thickness of thin materials, cuttings, or the like.

I6, and

My thickness measuring instrument requires no energization, and is readily portable, and it may be used at any time and place. It is adapted to effect thiclmess measurement with a high degree of accuracy and speed, and it may be used for a long period of time without necessity for any repair or replacement of any of its parts.

I have found that for a measurement of materials within the range` of thickness of twenty one-thousandths of an inch to thirty one-thousandths of an inch, no special adjustment of my device need be made.

My device may be embodied in gauges for measuring a thickness within the range of zero to fifty one-thousandths of an inch, with scale divisions of one-thousandth of an inch for each division. For ranges of greater thickness than -fty one-thousandths of an inch the sensitivity of the device increases somewhat.

Within a small portion of the scale the scale divisions may be proportional or of equal width; but for higher ranges the scale divisions should be spaced according to a logarithmic scale. The divisions are farther apart for low values and closer together for high values, which is highly desirable, as it facilitates the more accurate measurement of small increments,

The present gauges may also be used with curved surfaces, when equipped with the three legs and suitable calibration adjustments are made. When the device is equipped with limit contacts, it is also adapted to be used for automatic process control for the purpose of stopping the machine whenever the limits of thickness have been exceeded in either direction.

The present device may be used for detecting the presence of firearms or for detecting the presence of minute particles of magnetic material in the body, or in food products, and for locating pipes or conduits in walls.

While I have illustrated a preferred embodiment of my invention, many modications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction' set forth, but desire to avail myself of all changes within the scope ofthe appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a magnetic instrument the combination of a support with a permanent magnet having a pair of legs located adjacent each other and a thin pivotally mounted magnetic vane having its pivot vlocated outwardly of one of said legs in such manner that the vane is adapted to extend tangentially to the curved lines of magnetic force which extend from one leg to the other leg, said instrument being calibrated in terms of thickness and being arranged and constructed to measure the thickness of a member interposed between anauxiliary plate of magnetizable material and the ends of said permanent magnet, and said vane having indicatingmeans whereby the change in the direction of the lines of force may be indicated, one of said legs having an extension whereby it is longer than the other, and said longer leg having adjustable'means extending toward said vane whereby the direction of the vane may be controlled for effecting a zero correction of the indicator,

2. In a magnetic instrument the combination of .a support with a'permanent magnet having a pair of legs located adjacent each other and a thin pivotally mounted magnetic vane having its pivot located outwardly oi one of said legs in such manner that the vane is adapted to extend tangentially to the curved lines o! magnetic torce which extend from one leg to the other leg, said` instrument being calibratedl in terms of thickness and being arranged and constructed to measure the thickness of a member interposed between an auxiliary plate oi magnetizable material and the ends of said permanent magnet, and said vane having indicating means whereby the change in the direction oi' the lines of force may be indicated, said support having a pluralityV or legs for engagement with the work which is to be located between said legs and said plate ot magnetizable material.

3. In a magnetic instrument the combination of a support with a permanent magnet having a pair of legs located adjacent each other and a thin pivotally mounted magnetic vane having its pivot located outwardly of one of said legs in such in the direction of the une; of force may be in dicated, said support having a plurality oi' legs for engagement with the work which is to be located between said legs and said plate of magnetizable material. said legs being provided with hardened and rounded engaging surfaces ior measurement of thickness at a higher accuracy.

4. In a magnetic instrument the combination oi a support with a permanent magnet having a pair oi legs located adjacent each other and a thin pivotally mounted magnetic vane having its pivot located outwardly of one of said legs in such manner that the vane is adapted to extend tangentially to the curved lines of magnetic force which extend from one leg to the other leg. said instrument being calibrated in terms oi thickness and being arranged and constructed to measure the thickness. of a member interposed between an auxiliary plate of magnetizable material and the ends of said permanent magnet. and said vane having indicatingmeans whereby the change in the direction of the lines of force may be indicated, said support having a plurality oi legs for engagement with the work which is to be located between said legs and said plate of magnetizable material, one ot said legs being adjustably supported by threaded means.

VICTOR W. BREITEN STEIN. 

